Circadian rhythms and mood disorders: Time to see the light

Personal 24-hour light exposure pattern with obesity and adiposity-related parameters in school-aged children: A cross-sectional study based on compositional data analysis

The 24-h light exposure pattern is an essential feature of circadian rhythms and a potential contributor to body fat health. However, no previous studies have investigated 24-h light exposure patterns in relation to adiposity-related parameters in children. This cross-sectional study recruited school-aged children in Chuzhou, Anhui province, China. Personal 24-h light exposure was collected for 5 days and was divided into four measures: light at daytime (LAD)≥100 lx and <100 lx; light at night (LAN)≥1 lx and <1 lx. Adiposity-related parameters were measured via a body composition analyzer. The association of light exposure with adiposity-related parameters was analyzed using compositional data analysis (CoDA). This study included 831 children 8.53 ± 0.62 years, who were exposed to LAD≥100 lx for 490.1 ± 92.7 min and LAN≥1 lx for 311.2 ± 98.5 min. The proportion of time spent in LAD≥100 lx increasing by 1 % (14.4 min/day) was linked to a decline of 3.10 % in percentage of body fat (PBF). In contrast, prolonged exposure to LAN≥1 lx by 14.4 min/day was associated with an increase of 3.49 % in PBF (All P < 0.01). These associations were robust in boys after gender stratification. CoDA estimated that reducing the time of LAN≥1 lx had more influence in decreasing the odds of childhood overweight/obesity than increasing the time of LAD≥100 lx. Suboptimal 24-h light exposure patterns (brighter nights, darker days) play a threatening role in childhood overweight/obesity. Bright LAN replaced with darker LAN or bright LAD might help decrease the odds of childhood overweight/obesity.

Chronobiology of Mood Disorders: The Role of the biological clock in Depression and Bipolar Disorder

Mood disorders, including major depressive disorder (MDD), bipolar disorder (BD), and seasonal affective disorder (SAD), exhibit significant heterogeneity, with disturbances in biological rhythms playing a central role. These disturbances not only contribute to the onset and progression of mood disorders but also serve as important predictors of relapse (Chronos syndrome) and treatment response. Circadian disruptions, influenced by factors such as seasonality, jet lag, shift work, and childbirth, are hallmarks of mood episodes and pivotal in transitions between mood states. Longitudinal studies reveal a bidirectional relationship between circadian dysregulation and mood disorders, suggesting that biological clock abnormalities may both signal and predispose individuals to mood episodes. Despite their significance, no single circadian biomarker has demonstrated sufficient specificity or sensitivity for diagnostic precision. This underscores the urgent need for multimodal approaches that integrate circadian markers with other physiological and behavioral dimensions. Advancing mood disorder care requires biomarkers that capture individualized biological signatures, revealing circadian dysregulation and its interactions with multiple other physiological systems to enable precise subtyping and improved interventions. This review emphasizes the potential of integrating biological rhythms into a dimensional framework, leveraging advanced digital tools and mathematical models to provide ecologically valid insights into mood disorder mechanisms. Such approaches aim to bridge the gap between clinical observations and biological underpinnings, paving the way for biologically informed classifications and personalized treatment strategies. By addressing the complexity of circadian disruptions and their interplay with other systems, this paradigm shift offers a promising path to enhancing mood disorder diagnostics and therapeutics.

Bibliometric and visual analysis of circadian rhythms in depression from 2004 to 2024

INTRODUCTION

Understanding the intricate relationship between circadian rhythms and depression is crucial for developing effective interventions and treatments for individuals affected by depression. Circadian rhythms regulate various physiological and behavioral processes, while depression manifests as persistent feelings of sadness and disturbances in sleep, appetite, and energy levels. Emerging research suggests a significant interplay between circadian rhythm disruption and depression, highlighting the need for comprehensive analysis in this area.

METHODOLOGY

A bibliometric and visual analysis of literature on circadian rhythms in depression from 2004 to 2024 was conducted using the Web of Science Core Collection. Data were analyzed using bibliometric tools including VOSviewer, CiteSpace, and Bibliometrix to identify publication trends, geographical distribution, authorship patterns, institutional collaborations, journal preferences, keyword co-occurrence, and highly cited references.

RESULTS

Analysis revealed a steady increase in publications and citations related to circadian rhythms in depression. The United States emerged as the leading contributor, with strong global collaborations. Key journals included Chronobiology International and Journal of Affective Disorders. Top keywords included circadian rhythm, depression, sleep, melatonin, and bipolar disorder. The most cited article is a review titled "Practice parameters for the indications for polysomnography and related procedures: An update for 2005".

CONCLUSIONS

This study offers a comprehensive overview of research on circadian rhythms in depression, highlighting key trends, contributors, and interdisciplinary intersections.

B vitamins as adjunct therapies for depressive disorder

The rising prevalence of depressive disorder worldwide requires better interventional avenues. B vitamins are gaining increasing interest as potential therapeutic approaches in this context given current evidence for a bidirectional association between B vitamin deficiency and depressive disorder. We discuss how B vitamins and B vitamin-associated probiotic supplementation may represent an effective adjunctive treatment for depression, and highlight the key metabolic mechanisms involved. We also provide a perspective on the future of this field and advocate for further high-quality clinical trials to assess the benefits of B vitamins in this context and optimize their clinical implementation.

Association between eveningness and depressive symptoms in daytime workers: A cross-sectional analysis of the Aichi Workers' Cohort Study

Objectives

Eveningness (evening preference in chronotype) has been reported to be associated with a number of psychiatric problems. We examined a cross-sectional association between eveningness and depressive symptoms in daytime workers.

Methods

The subjects were 4410 civil servants (71.7% male, aged 18-69 years [mean, 43.5 years]) with no history of depressive disorder who did not perform shift work, and for whom there were no missing data. The association between eveningness, determined using the reduced Morningness-Eveningness Questionnaire, and depressive symptoms, determined using the shorter form of the Central Epidemiological Studies Depression scale, was assessed with logistic regression analysis adjusted for potential confounding factors (gender, income, living alone, breakfast intake, coffee consumption, drinking habits, exercise, smoking, working hours, sleep duration, and difficulty falling asleep).

Results

Of the subjects, 529 (12.0%) had eveningness, and 1408 (31.9%) reported depressive symptoms. Depressive symptoms were reported more frequently by those with eveningness than by those with other chronotypes (57.3% vs 28.5%). The association between eveningness and depression (gender- and age-adjusted odds ratio, 3.27; 95% confidence interval, 2.71-3.95) was significant after adjustment for the other confounding factors (odds ratio, 2.40; 95% confidence interval, 1.96-2.95).

Conclusions

Our results suggest that eveningness is associated with depressive symptoms among day workers and that this association is independent of potential confounding factors. Further longitudinal studies are needed to examine the causal relationship.

The effect of systematic antidepressant treatments in the early stages on sleep and impulsivity in bipolar euthymic patients: A cross-sectional study

BACKGROUND AND OBJECTIVES

Due to early misdiagnosis, bipolar patients who had a depressive episode as their initial onset often received systematic antidepressant treatments and continued to suffer from sleep disturbances and elevated impulsivity, even during euthymic state. The study aims to assess the effect of systematic antidepressant treatments in the early stages on sleep and impulsivity in bipolar euthymic patients, and further explore the potential mediating role of sleep in the relationship between early antidepressant uses and impulsivity.

METHODS

A total of 124 bipolar euthymic patients were enrolled. Based on the early use of antidepressants, patients were divided into AT group (systematic antidepressant treatment group) and NT group (no systematic antidepressant treatment group). Sleep quality and impulsivity were assessed using Pittsburgh Sleep Quality Index and Barratt Impulsivity Scale Questionnaire version 11, respectively. Statistical analyses were conducted using the t-test, Chi-square test, and Mann-Whitney U test, and mediation analysis was performed using bootstrapping.

RESULTS

Patients in the AT group showed poorer sleep quality and higher impulsivity than those in the NT group. Patients' sleep quality was positively correlated with impulsivity. Sleep quality mediated the relationship between antidepressant uses and impulsivity, including both overall impulsivity and non-planning impulsivity.

CONCLUSIONS

This study suggests a correlation between early-stage antidepressant use, sleep quality, and impulsivity of bipolar euthymic patients, highlighting the importance of early diagnosis of bipolar disorder and appropriate antidepressant prescriptions. Furthermore, improving sleep quality would be effective in reducing the risk of impulsive behaviors.

Associations between light at night and mental health: A systematic review and meta-analysis

Light at night (LAN) disrupts the circadian rhythm by altering the natural light-dark cycle. With increasing interest in the relationship between LAN and mental health, there is value in an updated systematic review and meta-analysis considering prominent mental health conditions that also critically appraises LAN exposure assessment. We conducted a systematic review of six databases, two registries, and Google Scholar to identify studies examining the associations between indoor and outdoor LAN exposure (high vs. low exposure) and mental health outcomes (depression, bipolar disorder, anxiety, and schizophrenia), completing inverse-variance random-effects meta-analyses. Nineteen studies with a total population of 556,861 were included in the review. LAN exposure was associated with increased odds of depression prevalence (odds ratio [OR]: 1.18; 95 % confidence interval [CI]: 1.09 to 1.28), with stronger associations for bedside (OR: 1.45; 95 % CI: 1.03 to 2.04) or wrist-measured indoor LAN (OR: 1.30; 95 % CI: 1.22 to 1.38) than satellite-measured outdoor LAN exposure (OR: 1.10; 95 % CI: 1.04 to 1.17) and in older adults (OR: 1.56; 95 % CI: 1.24 to 1.96) compared to general adults (OR: 1.16; 95 % CI: 1.06 to 1.28) or youth (OR: 1.07; 95 % CI: 0.99 to 1.16). LAN exposure was also associated with an increased prevalence of bipolar disorder (OR: 1.19; 95 % CI: 1.08 to 1.31) and anxiety (OR: 1.10; 95 % CI: 1.02 to 1.20) and increased incidence of anxiety (hazard ratio [HR]: 1.08; 95 % CI: 1.02 to 1.15) and schizophrenia (HR: 1.55; 95 % CI: 1.01 to 2.39); however, the incidence of depression did not achieve statistical significance (HR: 1.53; 95 % CI: 0.98 to 2.38). Overall, our results suggest that LAN exposure influences adverse mental health conditions, with differences in results appreciated for depression prevalence depending on how LAN exposure was measured. Additional research is needed on the effects of LAN given its undoubted interest in the prevention and treatment of mental disorders.

Circadian rhythm modulation in heart rate variability as potential biomarkers for major depressive disorder: A machine learning approach

Major depressive disorder (MDD) is associated with reduced heart rate variability (HRV), but its link to circadian rhythm modulation (CRM) of HRV is unclear. Given that depression disrupts circadian rhythms, assessing HRV fluctuations may better capture the CRM and the related autonomic nervous system (ANS) alterations, potentially enhancing our understanding of the pathophysiological mechanisms of MDD. This study aimed to explore the relationship between CRM of HRV and MDD, and to identify potential biomarkers for MDD using machine learning (ML). A total of 165 MDD patients and 60 healthy controls (HCs) were enrolled in the study, with each participant completing 24-h Holter electrocardiogram (ECG) monitoring and psychological scale assessments prior to receiving antidepressant treatment. The circadian rhythm of HRV was quantified using a cosine regression model, and seven typical ML models were employed to distinguish MDD from HCs. MDD patients exhibited a significant decrease in average diurnal HRV indices, particularly during night-time, along with reductions in the parameter M of HRV circadian rhythms compared to HCs. Depression severity was negatively associated with the parameters M of RMSSD, PNN50, HF, while positively associated with the parameter M of LF/HF ratio. Furthermore, the gradient boosting machine (GBM) model demonstrated the best performance in classifying MDD (accuracy 0.823, AUC 0.868), and a final GBM model was developed with 12 selected features. This study provides new insights into the relationship between circadian rhythm abnormalities and MDD, highlighting the potential of using CRM of HRV as novel biomarkers for MDD pathophysiology and clinical applications.

Nonlinear association between plasma elaidic acid level and sleep complaints in US adults: NHANES 2009-2010

Poor sleep is linked to an increased risk of metabolic, cardiovascular, psychiatric, and neurodegenerative diseases, highlighting its emergence as a public health concern. Previous studies demonstrated the harmful effects of trans fatty acids (TFAs) on human health. However, the association between TFAs and sleep outcomes is still not well-established. The current study aimed to investigate the relationship between plasma elaidic acid, a major TFA, and sleep complaints. The participants from the US National Health and Nutrition Examination Survey (NHANES) (2009-2010) were included. The plasma concentration of elaidic acid (18:1n-9t) was determined using the gas chromatography/mass spectrometry (GC/MS) method. The sleep outcome was defined based on the following questionnaire: "Ever told the doctor had trouble sleeping?" and "Ever told by a doctor have a sleep disorder?". Participants were classified as having sleep complaints if they ever told a doctor or been told by a doctor about trouble sleeping. The association between plasma elaidic acid and sleep complaints was investigated by multivariable logistic regressions, restricted cubic spline (RCS), and subgroup analysis. A total of 2068 participants were included, 561 of whom suffered from sleep complaints. The restricted cubic spline (RCS) regression analysis revealed a nonlinear (inverted L-shaped) relationship between plasma elaidic acid level and sleep complaints (p = 0.044), with an inflection point of 9.598 μmol/L. In the group with a low plasma elaidic acid level (≤9.598 μmol/L), there was a positive association between plasma elaidic acid level and the prevalence of sleep complaints (OR 1.28; 95% CI: 1.06-1.54, p = 0.01). When the plasma elaidic acid level was more than 9.598 μmol/L, the correlation was not statistically significant. Results were robust when analyses were stratified by sex, age, race, marital status, education level, family income, and BMI (all p for interaction >0.05). The results revealed a positive association between plasma elaidic acid and sleep complaints in US adults when plasma elaidic acid level ≤9.598 μmol. Given that the plasma TFA content has considerably declined in recent years, the detrimental impact of elaidic acid on sleep quality deserves more attention.

Two-photon activation, deactivation, and coherent control of melanopsin in live cells

Intrinsically photosensitive retinal ganglion cells are photoreceptors discovered in the last 20 years. These cells project to the suprachiasmatic nucleus of the brain to drive circadian rhythms, regulated by ambient light levels. The photopigment responsible for photoactivation in these cells, melanopsin, has been shown to exhibit many unique activation features among opsins. Notably, the photopigment can exist in three states dependent on the intensity and spectrum of ambient light, which affects its function. Despite increasing knowledge about these cells and melanopsin, tools that can manipulate their three states, and do so with single-cell precision, are limited. This reduces the extent to which circuit-level phenomena, and studying the implications of melanopsin tri-stability in living systems, can be pursued. In this report, we evoke and modulate calcium transients in live cells and intrinsically photosensitive retinal ganglion cells from isolated retinal tissues following two-photon excitation using near-infrared light pulses. We demonstrate that two-photon activation of melanopsin can successfully stimulate melanopsin-expressing cells with high spatio-temporal precision. Moreover, we demonstrate that the functional tri-stability of the photopigment can be interrogated by multiphoton excitation using spectral-temporal modulation of a broadband, ultrafast laser source.

From Stress to Synapse: The Neuronal Atrophy Pathway to Mood Dysregulation

Mood disorders, including major depressive disorder and bipolar disorder, are among the most prevalent mental health conditions globally, yet their underlying mechanisms remain incompletely understood. This review critically examines the neuronal atrophy hypothesis, which posits that chronic stress and associated neurobiological changes lead to structural and functional deficits in critical brain regions, contributing to mood disorder pathogenesis. Key mechanisms explored include dysregulation of neurotrophic factors such as brain-derived neurotrophic factor (BDNF), elevated glucocorticoids from stress responses, neuroinflammation mediated by cytokines, and mitochondrial dysfunction disrupting neuronal energy metabolism. These processes collectively impair synaptic plasticity, exacerbate structural atrophy, and perpetuate mood dysregulation. Emerging evidence from neuroimaging, genetic, and epigenetic studies underscores the complexity of these interactions and highlights the role of environmental factors such as early-life stress and urbanization. Furthermore, therapeutic strategies targeting neuroplasticity, including novel pharmacological agents, lifestyle interventions, and anti-inflammatory treatments, are discussed as promising avenues for improving patient outcomes. Advancing our understanding of the neuronal atrophy hypothesis could lead to more effective, sustainable interventions for managing mood disorders and mitigating their global health burden.

Suprachiasmatic nucleus dysfunction induces anxiety- and depression-like behaviors via activating the BDNF-TrkB pathway of the striatum

The circadian rhythm system consists of a master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus and peripheral clocks dispersed throughout other brain areas (including striatum, Str) as well as various tissues and organs. Circadian rhythm disturbance is a major risk factor and common comorbidity for mood disorders, especially anxiety and depression. Bmal1 is one of the fundamental clock protein genes that is required to maintain circadian rhythm. Recent research has revealed a link between suprachiasmatic nucleus dysfunction and anxiety and depression, but the underlying mechanisms remain to be fully elucidated. This study aimed to investigate how circadian rhythm disturbance may lead to anxiety- and depression-like behaviors. Through behavioral tests, virus tracing, molecular biology and other techniques, we found neural connection from the suprachiasmatic nucleus to the striatum. SCN lesions and Bmal1flox/flox + pAAV-hSyn-Cre-GFP (conditional knockout, cKO) mice exhibited disruptions in core body temperature rhythm, as well as anxiety- and depression-like behaviors. Importantly, these mice displayed altered expression patterns of clock protein genes and an upregulation of the Brain-Derived Neurotrophic Factor (BDNF) - Tyrosine Kinase receptor B (TrkB) signaling pathway within the striatum. Microinjection of the TrkB inhibitor ANA-12 can effectively reverse anxiety- and depression-like behaviors. These findings indicate that suprachiasmatic nucleus dysfunction may contribute to the pathogenesis of anxiety and depression through upregulation of the BDNF-TrkB pathway in the striatum, potentially mediated by neural projections from the SCN. Bmal1 gene within SCN may represent a novel therapeutic target for mood disorders.

Beyond vision: effects of light on the circadian clock and mood-related behaviours

Light is a crucial environmental factor that influences various aspects of life, including physiological and psychological processes. While light is well-known for its role in enabling humans and other animals to perceive their surroundings, its influence extends beyond vision. Importantly, light affects our internal time-keeping system, the circadian clock, which regulates daily rhythms of biochemical and physiological processes, ultimately impacting mood and behaviour. The 24-h availability of light can have profound effects on our well-being, both physically and mentally, as seen in cases of jet lag and shift work. This review summarizes the intricate relationships between light, the circadian clock, and mood-related behaviours, exploring the underlying mechanisms and its implications for health.

Clinical Chronobiology: Circadian Rhythms in Health and Disease

Circadian rhythms (CRs) are entrainable endogenous rhythms that respond to external stimuli and regulate physiological functions. The suprachiasmatic nucleus (SCN) in the hypothalamus is the mammalian master clock that synchronizes all other tissue-specific peripheral clocks, primarily through gamma-aminobutyric acid (GABA) and vasoactive intestinal polypeptide (VIP). The SCN follows Earth's 24-hour cycle by light entrainment through the retinohypothalamic tract. At the cellular level, the core clock genes CLOCK, BMAL1, PER1-PER3, CRY1, and CRY2 regulate CRs in a negative feedback loop. The circadian disruption of the sleep-wake cycle manifests in at least six distinct clinical conditions. These are the circadian rhythm sleep-wake disorders (CRSWDs). Their diagnosis is made by history, sleep diaries, and actigraphy. Treatment involves a combination of timed light exposure, melatonin/melatonin agonists, and behavioral interventions. In addition, CR disturbances and subsequent misalignment can increase the risk of a variety of illnesses. These include infertility and menstrual irregularities as well as diabetes, obesity, fatty liver disease, and other metabolic syndromes. In addition, a disruption in the gut microbiome creates a proinflammatory environment. CR disturbances increase the risk for mood disorders, hence the utility of light-based therapies in depression. People with neurodegenerative disorders demonstrate significant disturbances in their CRs, and in their sleep-wake cycles. Circadian realignment therapies can also help decrease the symptomatic burden of these disorders. Certain epilepsy syndromes, such as juvenile myoclonic epilepsy (JME), have a circadian pattern of seizures. Circadian disturbances in epilepsy can be both the consequence and cause for breakthrough seizures. The immune system has its own CR. Disturbances in these due to shift work, for instance, can increase the risk of infections. CR disturbances can also increase the risk of cancer by impacting DNA repair, apoptosis, immune surveillance, and cell cycle regulation. Moreover, the timing of chemotherapeutic agents has been shown to increase their therapeutic impact in certain cancers.

Pharmaceutical 3D Printing Technology Integrating Nanomaterials and Nanodevices for Precision Neurological Therapies

Pharmaceutical 3D printing, combined with nanomaterials and nanodevices, presents a transformative approach to precision medicine for treating neurological diseases. This technology enables the creation of tailored dosage forms with controlled release profiles, enhancing drug delivery across the blood-brain barrier (BBB). The integration of nanoparticles, such as poly lactic-co-glycolic acid (PLGA), chitosan, and metallic nanomaterials, into 3D-printed scaffolds improves treatment efficacy by providing targeted and prolonged drug release. Recent advances have demonstrated the potential of these systems in treating conditions like Parkinson's disease, epilepsy, and brain tumors. Moreover, 3D printing allows for multi-drug combinations and personalized formulations that adapt to individual patient needs. Novel drug delivery approaches, including stimuli-responsive systems, on-demand dosing, and theragnostics, provide new possibilities for the real-time monitoring and treatment of neurological disorders. Despite these innovations, challenges remain in terms of scalability, regulatory approval, and long-term safety. The future perspectives of this technology suggest its potential to revolutionize neurological treatments by offering patient-specific therapies, improved drug penetration, and enhanced treatment outcomes. This review discusses the current state, applications, and transformative potential of 3D printing and nanotechnology in neurological treatment, highlighting the need for further research to overcome the existing challenges.

The crosstalk between CREB and PER2 mediates the transition between mania- and depression-like behavior

Bipolar disorder (BD) is a severe psychiatric disorder characterized by alternating manic and depressive episodes. The molecular mechanisms underlying the transition between mania and depression remain unclear. Utilizing a mania animal model induced by ouabain, we observed reduced phosphorylated level of cyclic AMP-responsive element-binding protein (pCREB) and Period (PER)2 expression in the cornu ammonis (CA1) region of the hippocampus, which were restored by lithium treatment. shRNA knockdown of CREB or Per2 in CA1 region induced mania-like behavior, while overexpression of both factors resulted in depression-like behavior. Furthermore, our protein analyses revealed that the upregulation or downregulation of CREB or Per2 influenced each other's expression. Co-immunoprecipitation results demonstrated that CREB interacts with PER2. Taken together, our data suggest for potential inter-regulatory crosstalk between CREB-PER2 in hippocampal CA1 region, which mediates the transition between mania- and depression-like behaviors.

Conventional and new immunotherapies for immune system dysregulation in postpartum mood disorders: comparisons to immune system dysregulations in bipolar disorder, major depression, and postpartum autoimmune thyroid disease

INTRODUCTION

Postpartum mood disorders are heterogenous disorders and comprise postpartum psychosis and postpartum depression. Evidence is accumulating that systemic monocyte/macrophage activation, low-grade inflammation and (premature senescence related) T cell defects increase the risk for mood disorders outside pregnancy by affecting the function of microglia and T cells in the emotional brain (the cortico-limbic system) leading to inadequate mood regulation upon stress.

AREAS COVERED

The evidence in the literature that similar immune dysregulations are present in postpartum mood disorders.

RESULTS

The physiological postpartum period is characterized by a rapid T cell surge and a mild activation of the monocyte/macrophage system. Postpartum mood disorder patients show a diminished T cell surge (including that of T regulatory cells) and an increase in low grade inflammation, that is, an increased inflammatory state of monocytes/macrophages and higher levels of serum pro-inflammatory cytokines.

EXPERT OPINION

Anti-inflammatory agents (e.g. COX-2 inhibitors) and T cell boosting agents (e.g. low-dose IL-2 therapy) should be further investigated as treatment. The hypothesis should be investigated that postpartum mood disorders are active episodes (triggered by changes in the postpartum immuno-endocrine milieu) in ongoing, dynamically fluctuating aberrant neuro-immune-endocrine trajectories leading to mood disorders in women (inheritably) vulnerable to these disorders.

Circadian phase instability in bipolar disorder: a neglected essence

Circadian system disruption is an essential but poorly understood feature of bipolar disorder (BD) and associated comorbidities. This forum article summarizes current evidence regarding the emerging concept of circadian phase instability (CPI) as a neglected phenomenon with possibly unique features in BD that could be harnessed to develop individually tailored chronobiological interventions.

Differential serum levels of CACNA1C, circadian rhythm and stress response molecules in subjects with bipolar disorder: Associations with genetic and clinical factors

BACKGROUND

Many patients with bipolar disorder (BD) do not respond to or have difficulties tolerating lithium and/or other mood stabilizing agents. There is a need for personalized treatments based on biomarkers in guiding treatment options. The calcium voltage-gated channel CACNA1C is a promising candidate for developing personalized treatments. CACNA1C is implicated in BD by genome-wide association studies and several lines of evidence suggest that targeting L-type calcium channels could be an effective treatment strategy. However, before such individualized treatments can be pursued, biomarkers predicting treatment response need to be developed.

METHODS

As a first step in testing the hypothesis that CACNA1C genotype is associated with serum levels of CACNA1C, we conducted ELISA measures on serum samples from 100 subjects with BD and 100 control subjects.

RESULTS

We observed significantly higher CACNA1C (p < 0.01) protein levels in subjects with BD. The risk single nucleotide polymorpshism (SNP) (rs11062170) showed functional significance as subjects homozygous for the risk allele (CC) had significantly greater CACNA1C protein levels compared to subjects with one (p = 0.013) or no copies (p = 0.009). We observed higher somatostatin (SST) (p < 0.003) protein levels and lower levels of the clock protein aryl hydrocarbon receptor nuclear translocator-like (ARTNL) (p < 0.03) and stress signaling factor corticotrophin releasing hormone (CRH) (p < 0.001) in BD. SST and period 2 (PER2) protein levels were associated with both alcohol dependence and lithium response.

CONCLUSIONS

Our findings represent the first evidence for increased serum levels of CACNA1C in BD. Along with altered levels of SST, ARNTL, and CRH our findings suggest CACNA1C is associated with circadian rhythm and stress response disturbances in BD.

The Use of Melatoninergic Antidepressants for Stabilization of Remission in Depression Comorbid with Alcohol Abuse, Anxiety or Neuropsychiatric Disorders: A Systematic Review

BACKGROUND

Depression is one of the most common mental disorders and is associated with a significant increase in the risk of mental and somatic comorbidities. The chronobiological theory of the pathogenesis of depression explains the relationship between the symptoms of depression and disturbance of circadian rhythm regulation. Disrupted circadian rhythms are also observed in other disorders such as alcohol use disorder, anxiety disorders, epilepsy, and Parkinson's disease. Therefore, there is a growing interest in the use of medications with a melatoninergic mechanism of action in the treatment of depression comorbid with the aforementioned disorders.

AIM

This review aims to systematically examine the evidence for the use of melatoninergic antidepressants (agomelatine and fluvoxamine) in the treatment of depression comorbid with alcohol abuse, anxiety disorders (including phobic anxiety, panic, and generalized anxiety disorders), or neuropsychiatric disorders (such as epilepsy and Parkinson's disease).

METHODS

This systematic review included experimental studies, systematic reviews, and meta-analyses published in English and Russian, which examined the use of fluvoxamine and agomelatine in adult patients with recurrent depressive disorder (ICD-10) or major depressive disorder (DSM-5) comorbid with alcohol abuse, anxiety or neuropsychiatric disorders. The search was conducted in the PubMed, Cochrane Library and eLIBRARY scientific databases. The quality of the selected studies was assessed using the Cochrane Risk of Bias tool, which is used to evaluate the risk of systematic errors in clinical studies. The results were presented as a narrative synthesis and grouped by the comorbidities evaluated.

RESULTS

A total of 20 articles were reviewed (with a pooled sample size of n=1,833 participants). The results suggest that melatoninergic antidepressants might help in reducing depressive and anxiety symptoms, improve sleep, decrease alcohol cravings, and alleviate the severity of motor symptoms in Parkinson's disease. Moreover, the use of pharmacogenetic testing to select the medication and dosage may enhance its therapeutic effectiveness.

CONCLUSION

The review demonstrates a significant lack of clinical data and guidelines on the use of melatoninergic medications for the treatment of depression comorbid with other disorders. In this regard, it is currently difficult to draw a definitive conclusion regarding the efficacy and safety of agomelatine and fluvoxamine in the treatment of these comorbidities. Available studies suggest an improvement in the clinical manifestations of the comorbidities. Future research directions might include the development and implementation of double-blind, randomized clinical trials to study the use of melatoninergic medications in patients with depression comorbid with other disorders.

Accurately predicting mood episodes in mood disorder patients using wearable sleep and circadian rhythm features

Wearable devices enable passive collection of sleep, heart rate, and step-count data, offering potential for mood episode prediction in mood disorder patients. However, current models often require various data types, limiting real-world application. Here, we develop models that predict future episodes using only sleep-wake data, easily gathered through smartphones and wearables when trained on an individual's sleep-wake history and past mood episodes. Using mathematical modeling to longitudinal data from 168 patients (587 days average clinical follow-up, 267 days wearable data), we derived 36 sleep and circadian rhythm features. These features enabled accurate next-day predictions for depressive, manic, and hypomanic episodes (AUCs: 0.80, 0.98, 0.95). Notably, daily circadian phase shifts were the most significant predictors: delays linked to depressive episodes, advances to manic episodes. This prospective observational cohort study (ClinicalTrials.gov: NCT03088657, 2017-3-23) shows sleep-wake data, combined with prior mood episode history, can effectively predict mood episodes, enhancing mood disorder management.

Is There such a Thing as Post-Viral Depression?: Implications for Precision Medicine

Viral infections are increasingly recognized as triggers for depressive disorders, particularly following the SARS-CoV-2 pandemic and the rise of long COVID. Viruses such as Herpes Simplex Virus (HSV), Epstein-Barr Virus (EBV), Cytomegalovirus (CMV), and Human Immunodeficiency Virus (HIV) are linked to depression through complex neurobiological mechanisms. These include immune system dysregulation, chronic inflammation, and neurotransmitter imbalances that affect brain function and mood regulation. Viral activation of the immune system leads to the release of pro-inflammatory cytokines, resulting in neuroinflammation and associated depressive symptoms. Furthermore, specific viruses can disrupt neurotransmitter systems, including serotonin, dopamine, and glutamate, all of which are essential for mood stabilization. The unique interactions of different viruses with these systems underscore the need for virus-specific therapeutic approaches. Current broad-spectrum treatments often overlook the precise neurobiological pathways involved in post-viral depression, reducing their efficacy. This review emphasizes the need to understand these virus-specific interactions to create tailored interventions that directly address the neurobiological effects induced by each type of virus. These interventions may include immunomodulatory treatments that target persistent inflammation, antiviral therapies to reduce the viral load, or neuroprotective strategies that restore neurotransmitter balance. Precision medicine offers promising avenues for the effective management of virus-induced depression, providing patient-specific approaches that address the specific biological mechanisms involved. By focusing on the development of these targeted treatments, this review aims to pave the way for a new era in psychiatric care that fully addresses the root causes of depression induced by viral infections.

The putative role of the habenula in animal migration

BACKGROUND

When an addicted animal seeks a specific substance, it is based on the perception of internal and external cues that strongly motivate to pursue the acquisition of that compound. In essence, a similar process acts out when an animal leaves its present area to begin its circannual migration. This review article examines the existence of scientific evidence for possible relatedness of migration and addiction by influencing Dorsal Diencephalic Conduction System (DDCS) including the habenula.

METHODS

For this review especially the databases of Pubmed and Embase were frequently and non-systematically searched.

RESULTS

The mechanisms of bird migration have been thoroughly investigated. Especially the mechanism of the circannual biorhythm and its associated endocrine regulation has been well elucidated. A typical behavior called "Zugunruhe" marks the moment of leaving in migratory birds. The role of magnetoreception in navigation has also been clarified in recent years. However, how bird migration is regulated at the neuronal level in the forebrain is not well understood. Among mammals, marine mammals are most similar to birds. They use terrestrial magnetic field when navigating and often bridge long distances between breeding and foraging areas. Population migration is further often seen among the large hoofed mammals in different parts of the world. Importantly, learning processes and social interactions with conspecifics play a major role in these ungulates. Considering the evolutionary development of the forebrain in vertebrates, it can be postulated that the DDCS plays a central role in regulating the readiness and intensity of essential (emotional) behaviors. There is manifold evidence that this DDCS plays an important role in relapse to abuse after prolonged periods of abstinence from addictive behavior. It is also possible that the DDCS plays a role in navigation.

CONCLUSIONS

The role of the DDCS in the neurobiological regulation of bird migration has hardly been investigated. The involvement of this system in relapse to addiction in mammals might suggest to change this. It is recommended that particularly during "Zugunruhe" the role of neuronal regulation via the DDCS will be further investigated.

Sulforaphane Improves Liver Metabolism and Gut Microbiota in Circadian Rhythm Disorder Mice Models Fed With High-Fat Diets

SCOPE

This study aims to investigate the effect of sulforaphane (SFN) on hepatic metabolism and gut microbiota in a shifted circadian rhythm (CR) mouse model fed with a high-fat diet (HFD).

METHODS AND RESULTS

A shifted CR mouse model with HFD is constructed. Biochemical analyses are used to evaluate the effects of SFN on lipid accumulation and liver function. Targeted metabolomics is used for liver metabolites. Results from hematoxylin and eosin staining and Oil Red O staining show that SFN improves liver lipid accumulation and intestinal inflammatory damage in shifted CR treatment with HFD. The concentrations of amino acid metabolites are increased, and the levels of bile acid metabolites are significantly decreased by SFN treatment. Results from 16S rRNA gene sequencing indicate that SFN modulates gut microbiota, particularly by enhancing beneficial bacteria such as Lachnospiraceae, Lactobacillus, Alistipes, Akkermansia, and Eubacteriaum coprostanoligenes. Correlation analysis confirms a close relationship between intestinal microbiota and hepatic metabolites. SFN significantly regulates CR protein expression in the hypothalamus and liver tissues.

CONCLUSION

SFN alleviates hepatic metabolic disorder and gut microbiota dysbiosis induced by CR disruption under a high-fat diet in a mouse model, indicating the potential of SFN in regulating CR disruption.

NEK4 modulates circadian fluctuations of emotional behaviors and synaptogenesis in male mice

GWASs have linked the 3p21.1 locus, which is associated with the expression levels of NEK4, to bipolar disorder. Here, we use integrative analyses of GWAS statistics and eQTL annotations to establish that elevated NEK4 expression in the hippocampus is associated with an increased risk of bipolar disorder. To further study this association, we generate transgenic male mice that conditionally overexpress NEK4 in the pyramidal neurons of the adult forebrain, or use AAV to overexpress NEK4 in the dorsal hippocampus. Compared to the control mice, male mice of both strains exhibit a shift from a diurnal anxiety state to a nocturnal normal or anxiolytic-like state. Overexpression of NEK4 also affects the circadian fluctuations in dendritic spine morphology and synaptic structure. Furthermore, we show that treatment with lithium ameliorates the effects of NEK4 overexpression in male mice. We then perform phosphoproteomic analyses to demonstrate that the diurnal and nocturnal phosphoproteomic profiles of male control and NEK4 overexpressing mice are different. These results suggest that male mice with different NEK4 expression levels may recapitulate some of the core features observed in patients with bipolar disorder, indicating that interruption of the homeostatic dynamics of synapses may underlie the emotional swings in bipolar disorder.

Circadian Rhythms Tied to Changes in Brain Morphology in a Densely Sampled Male

Circadian, infradian, and seasonal changes in steroid hormone secretion have been tied to changes in brain volume in several mammalian species. However, the relationship between circadian changes in steroid hormone production and rhythmic changes in brain morphology in humans is largely unknown. Here, we examined the relationship between diurnal fluctuations in steroid hormones and multiscale brain morphology in a precision imaging study of a male who completed 40 MRI and serological assessments at 7 A.M. and 8 P.M. over the course of a month, targeting hormone concentrations at their peak and nadir. Diurnal fluctuations in steroid hormones were tied to pronounced changes in global and regional brain morphology. From morning to evening, total brain volume, gray matter volume, and cortical thickness decreased, coincident with decreases in steroid hormone concentrations (testosterone, estradiol, and cortisol). In parallel, cerebrospinal fluid and ventricle size increased from A.M. to P.M. Global changes were driven by decreases within the occipital and parietal cortices. These findings highlight natural rhythms in brain morphology that keep time with the diurnal ebb and flow of steroid hormones.

A translationally informed approach to vital signs for psychiatry: a preliminary proof of concept

The nature of data obtainable from the commercial smartphone - bolstered by a translational model emphasizing the impact of social and physical zeitgebers on circadian rhythms and mood - offers the possibility of scalable and objective vital signs for major depression. Our objective was to explore associations between passively sensed behavioral smartphone data and repeatedly measured depressive symptoms to suggest which features could eventually lead towards vital signs for depression. We collected continuous behavioral data and bi-weekly depressive symptoms (PHQ-8) from 131 psychiatric outpatients with a lifetime DSM-5 diagnosis of depression and/or anxiety over a 16-week period. Using linear mixed-effects models, we related depressive symptoms to concurrent passively sensed behavioral summary features (mean and variability of sleep, activity, and social engagement metrics), considering both between- and within-person associations. Individuals with more variable wake-up times across the study reported higher depressive symptoms relative to individuals with less variable wake-up times (B [95% CI] = 1.53 [0.13, 2.93]). On a given week, having a lower step count (-0.16 [-0.32, -0.01]), slower walking rate (-1.46 [-2.60, -0.32]), lower normalized location entropy (-3.01 [-5.51, -0.52]), more time at home (0.05 [0.00, 0.10]), and lower distances traveled (-0.97 [-1.72, -0.22]), relative to one's own typical levels, were each associated with higher depressive symptoms. With replication in larger samples and a clear understanding of how these components are best combined, a behavioral composite measure of depression could potentially offer the kinds of vital signs for psychiatric medicine that have proven invaluable to assessment and decision-making in physical medicine. Clinical Trials Registration: The data that form the basis of this report were collected as part of clinical trial number NCT03152864.

The Nested States Model: A Phenomenologically-Grounded Model of the Mind

BACKGROUND

Subjective experience is central to the nature of mental illness, yet it has not played a central role in most empirical approaches to psychopathology. While phenomenological perspectives in psychiatry have seen a recent resurgence, there remains a need for more detailed models of psychopathological processes based on explicit phenomenological and enactive foundations.

SUMMARY

We present a framework derived from the Nested States Model (NSM) through which such phenomenologically-grounded models might be constructed. The NSM describes the dynamic structure of subjective experience as a system of nested states that reciprocally influence one another across hierarchical layers. Here, we show how the NSM provides a scheme for characterizing patterns of experience that comprise various psychopathological processes. We demonstrate the utility of this scheme both for clinical practice and for building our knowledge of psychopathological processes more broadly.

KEY MESSAGES

The NSM can advance three aims that we see as critical for the lasting integration of phenomenological approaches to psychopathology within psychiatry. First, we show that the NSM provides a means for constructing clinical formulations and treatment considerations that center squarely on an individual's subjective experiences. Second, the NSM supplies a framework for organizing findings from clinical-phenomenological research that can guide the construction of broader phenomenologically-grounded models of psychopathological processes. Lastly, the NSM aligns our perspective on subjective experience with emerging perspectives on brain dynamics, helping to bridge phenomenological work with ongoing neurophysiological research.

Chinese self-report version of biological rhythms interview for assessment in neuropsychiatry (C-BRIAN-SR) - psychometric properties and prospective follow-up in patients with non-seasonal depression

This study examined the psychometric properties and longitudinal changes of the self-reporting Traditional Chinese version of Biological Rhythms Interview for Assessment in Neuropsychiatry (C-BRIAN-SR) among healthy controls (HC) and patients with major depressive episode (MDE). Eighty patients with a current MDE and 80 HC were recruited. Assessments were repeated after two weeks in HC, and upon the discharge of MDE patients to examine the prospective changes upon remission of depression. The C-BRIAN-SR score was significantly higher in the MDE than HC group. The concurrent validity was supported by a positive correlation between scores of C-BRIAN-SR, Insomnia Severity Index and the Hospital Anxiety Depression Scale. C-BRIAN-SR negatively correlated MEQ in the MDE group (r = .30, p = 0.009), suggesting higher rhythm disturbances were associated with a tendency toward eveningness. A moderate test-retest reliability was found (r = .61, p < 0.001). A cut-off of 38.5 distinguished MDE subjects from HC with 82.9% of sensitivity and 81.0% of specificity. C-BRIAN-SR score normalized in remitted MDE patients but remained higher in the non-remitted. The C-BRIAN-SR is a valid and reliable scale for measuring the biological rhythms and may assist in the screening of patients with MDE.

Exploring the interplay between circadian rhythms and prostate cancer: insights into androgen receptor signaling and therapeutic opportunities

Circadian rhythm disruption is closely related to increased incidence of prostate cancer. Incorporating circadian rhythms into the study of prostate cancer pathogenesis can provide a more comprehensive understanding of the causes of cancer and offer new options for precise treatment. Therefore, this article comprehensively summarizes the epidemiology of prostate cancer, expounds the contradictory relationship between circadian rhythm disorders and prostate cancer risk, and elucidates the relationship between circadian rhythm regulators and the incidence of prostate cancer. Importantly, this article also focuses on the correlation between circadian rhythms and androgen receptor signaling pathways, as well as the applicability of time therapy in prostate cancer. This may prove significant in enhancing the clinical treatment of prostate cancer.

Mining key circadian biomarkers for major depressive disorder by integrating bioinformatics and machine learning

OBJECTIVE

This study aimed to identify key clock genes closely associated with major depressive disorder (MDD) using bioinformatics and machine learning approaches.

METHODS

Gene expression data of 128 MDD patients and 64 healthy controls from blood samples were obtained. Differentially expressed were identified and weighted gene co-expression network analysis (WGCNA) was first performed to screen MDD-related key genes. These genes were then intersected with 1475 known circadian rhythm genes to identify circadian rhythm genes associated with MDD. Finally, multiple machine learning algorithms were applied for further selection, to determine the most critical 4 circadian rhythm biomarkers.

RESULTS

Four key circadian rhythm genes (ABCC2, APP, HK2 and RORA) were identified that could effectively distinguish MDD samples from controls. These genes were significantly enriched in circadian pathways and showed strong correlations with immune cell infiltration. Drug target prediction suggested that small molecules like melatonin and escitalopram may target these circadian rhythm proteins.

CONCLUSION

This study revealed discovered 4 key circadian rhythm genes closely associated with MDD, which may serve as diagnostic biomarkers and therapeutic targets. The findings highlight the important roles of circadian disruptions in the pathogenesis of MDD, providing new insights for precision diagnosis and targeted treatment of MDD.

The Relationship between Circadian Rhythm and Cancer Disease

The circadian clock regulates biological cycles across species and is crucial for physiological activities and biochemical reactions, including cancer onset and development. The interplay between the circadian rhythm and cancer involves regulating cell division, DNA repair, immune function, hormonal balance, and the potential for chronotherapy. This highlights the importance of maintaining a healthy circadian rhythm for cancer prevention and treatment. This article investigates the complex relationship between the circadian rhythm and cancer, exploring how disruptions to the internal clock may contribute to tumorigenesis and influence cancer progression. Numerous databases are utilized to conduct searches for articles, such as NCBI, MEDLINE, and Scopus. The keywords used throughout the academic archives are "circadian rhythm", "cancer", and "circadian clock". Maintaining a healthy circadian cycle involves prioritizing healthy sleep habits and minimizing disruptions, such as consistent sleep schedules, reduced artificial light exposure, and meal timing adjustments. Dysregulation of the circadian clock gene and cell cycle can cause tumor growth, leading to the need to regulate the circadian cycle for better treatment outcomes. The circadian clock components significantly impact cellular responses to DNA damage, influencing cancer development. Understanding the circadian rhythm's role in tumor diseases and their therapeutic targets is essential for treating and preventing cancer. Disruptions to the circadian rhythm can promote abnormal cell development and tumor metastasis, potentially due to immune system imbalances and hormonal fluctuations.

Circadian rhythms tied to changes in brain morphology in a densely-sampled male

Circadian, infradian, and seasonal changes in steroid hormone secretion have been tied to changes in brain volume in several mammalian species. However, the relationship between circadian changes in steroid hormone production and rhythmic changes in brain morphology in humans is largely unknown. Here, we examined the relationship between diurnal fluctuations in steroid hormones and multiscale brain morphology in a precision imaging study of a male who completed forty MRI and serological assessments at 7 A.M. and 8 P.M. over the course of a month, targeting hormone concentrations at their peak and nadir. Diurnal fluctuations in steroid hormones were tied to pronounced changes in global and regional brain morphology. From morning to evening, total brain volume, gray matter volume, and cortical thickness decreased, coincident with decreases in steroid hormone concentrations (testosterone, estradiol, and cortisol). In parallel, cerebrospinal fluid and ventricle size increased from A.M. to P.M. Global changes were driven by decreases within the occipital and parietal cortices. These findings highlight natural rhythms in brain morphology that keep time with the diurnal ebb and flow of steroid hormones.

Higher Seasonal Variation of Systemic Inflammation in Bipolar Disorder

Seasonal rhythms affect the immune system. Evidence supports the involvement of immuno-inflammatory mechanisms in bipolar disorder (BD), with the neutrophil to lymphocyte ratio (NLR), and the systemic immune-inflammatory index (SII; platelets × neutrophils/lymphocytes) consistently reported to be higher in patients with BD than in HC, but seasonal rhythms of innate and adaptive immunity have never been studied. We retrospectively studied NLR and SII in 824 participants divided into three groups: 321 consecutively admitted inpatients affected by a major depressive episode in course of BD, and 255 consecutively admitted inpatients affected by obsessive-compulsive disorder (OCD; positive psychiatric control), and 248 healthy controls (HC). Patients with BD showed markedly higher markers of systemic inflammation in autumn and winter, but not in spring and summer, in respect to both HC and patients with OCD, thus suggesting a specific effect of season on inflammatory markers in BD, independent of a shared hospital setting and drug treatment. Given that systemic inflammation is emerging as a new marker and as target for treatment in depressive disorders, we suggest that seasonal rhythms should be considered for tailoring antidepressant immuno-modulatory treatments in a precision medicine approach.

Differential Serum Levels of CACNA1C, Circadian Rhythm and Stress Response Molecules in Subjects with Bipolar Disorder: Associations with Genetic and Clinical Factors

Background

Many patients with bipolar disorder (BD) do not respond to or have difficulties tolerating lithium and/or other mood stabilizing agents. There is a need for personalized treatments based on biomarkers in guiding treatment options. The calcium voltage-gated channel CACNA1C is a promising candidate for developing personalized treatments. CACNA1C is implicated in BD by genome-wide association studies and several lines of evidence suggest that targeting L-type calcium channels could be an effective treatment strategy. However, before such individualized treatments can be pursued, biomarkers predicting treatment response need to be developed.

Methods

As a first step in testing the hypothesis that CACNA1C genotype is associated with serum levels of CACNA1C, we conducted ELISA measures on serum samples from 100 subjects with BD and 100 control subjects.

Results

We observed significantly higher CACNA1C (p<0.01) protein levels in subjects with BD. The risk SNP (rs11062170) showed functional significance as subjects homozygous for the risk allele (CC) had significantly greater CACNA1C protein levels compared to subjects with one (p=0.013) or no copies (p=0.009). We observed higher somatostatin (SST) (p<0.003) protein levels and lower levels of the clock protein ARTNL (p<0.03) and stress signaling factor corticotrophin releasing hormone (CRH) (p<0.001) in BD. SST and PER2 protein levels were associated with both alcohol dependence and lithium response.

Conclusions

Our findings represent the first evidence for increased serum levels of CACNA1C in BD. Along with altered levels of SST, ARNTL, and CRH our findings suggest CACNA1C is associated with circadian rhythm and stress response disturbances in BD.

The missing hallmark of health: psychosocial adaptation

The eight biological hallmarks of health that we initially postulated (Cell. 2021 Jan 7;184(1):33-63) include features of spatial compartmentalization (integrity of barriers, containment of local perturbations), maintenance of homeostasis over time (recycling & turnover, integration of circuitries, rhythmic oscillations) and an array of adequate responses to stress (homeostatic resilience, hormetic regulation, repair & regeneration). These hallmarks affect all eight somatic strata of the human body (molecules, organelles, cells, supracellular units, organs, organ systems, systemic circuitries and meta-organism). Here we postulate that mental and socioeconomic factors must be added to this 8×8 matrix as an additional hallmark of health ("psychosocial adaptation") and as an additional stratum ("psychosocial interactions"), hence building a 9×9 matrix. Potentially, perturbation of each of the somatic hallmarks and strata affects psychosocial factors and vice versa. Finally, we discuss the (patho)physiological bases of these interactions and their implications for mental health improvement.

The cognitive impact of light: illuminating ipRGC circuit mechanisms

Ever-present in our environments, light entrains circadian rhythms over long timescales, influencing daily activity patterns, health and performance. Increasing evidence indicates that light also acts independently of the circadian system to directly impact physiology and behaviour, including cognition. Exposure to light stimulates brain areas involved in cognition and appears to improve a broad range of cognitive functions. However, the extent of these effects and their mechanisms are unknown. Intrinsically photosensitive retinal ganglion cells (ipRGCs) have emerged as the primary conduit through which light impacts non-image-forming behaviours and are a prime candidate for mediating the direct effects of light on cognition. Here, we review the current state of understanding of these effects in humans and mice, and the tools available to uncover circuit-level and photoreceptor-specific mechanisms. We also address current barriers to progress in this area. Current and future efforts to unravel the circuits through which light influences cognitive functions may inform the tailoring of lighting landscapes to optimize health and cognitive function.

Circadian lifestyle determinants of immune checkpoint inhibitor efficacy

Immune Checkpoint Inhibitors (ICI) have revolutionised cancer care in recent years. Despite a global improvement in the efficacy and tolerability of systemic anticancer treatments, a sizeable proportion of patients still do not benefit maximally from ICI. Extensive research has been undertaken to reveal the immune- and cancer-related mechanisms underlying resistance and response to ICI, yet more limited investigations have explored potentially modifiable lifestyle host factors and their impact on ICI efficacy and tolerability. Moreover, multiple trials have reported a marked and coherent effect of time-of-day ICI administration and patients' outcomes. The biological circadian clock indeed temporally controls multiple aspects of the immune system, both directly and through mediation of timing of lifestyle actions, including food intake, physical exercise, exposure to bright light and sleep. These factors potentially modulate the immune response also through the microbiome, emerging as an important mediator of a patient's immune system. Thus, this review will look at critically amalgamating the existing clinical and experimental evidence to postulate how modifiable lifestyle factors could be used to improve the outcomes of cancer patients on immunotherapy through appropriate and individualised entrainment of the circadian timing system and temporal orchestration of the immune system functions.